Planetesimal rotations induced by collisions

Abstract

Collision events between celestial bodies on prograde orbits in a Keplerian disc produce an excess of prograde rotations because of the geometry of the shocks. Circular orbits produce prograde rotations in 80 % of the cases. With a simple collision law based on some friction of the surfaces, the rotation increment is found to be roughly proportional to R− 1, 36 on a circular path of radius R. Nearly tangent eccentric orbits induce larger prograde rotations but reduce the collisions frequencies. Crossing orbits generate both prograde and retrograde rotations with an excess of prograde ones.